It is well known in the manufacture of most mechanical devices that the degree of accuracy to which any mechanical device is constructed may be controlled according to the tolerance level or margin of error to which the various parts of the device are constructed. Various matters, such as quality of surface finish, type of material, character of heat treating, etc. are largely determinative not only of the quality of the mechanical device, but also these factors affect the cost of manufacturing of such devices. In fact, costs of manufacturing in most circumstances appear to be reflected by the character of manufacturing tolerances and materials to an exponential degree. In other words, manufacturing costs rise exponentially with improvement of the quality of most mechanical devices. In most circumstances, however, there is a limit to the quality of any particular product, depending upon the purchasers use of that particular product and the price the purchaser is willing to pay for the product.
In the field of flow meter manufacture the foregoing holds true, because manufacturing costs appear to be exponentially related to the quality of machining operations, quality of bearings and other parts as well as the quality of the material that is utilized in the manufacturing process. It is desirable, however, to provide a flow meter construction, especially for flowing liquid, that is extremely sensitive to all conditions of flow and provides as accurate a readout of the volume of flowing liquid as is practical. This factor holds true regardless of the particular type of flow meter involved.
Although the present invention may find effective application in various types of flow meter constructions, for the purpose of simplicity and to facilitate ready understanding of the present invention, the invention will be set forth herein particularly as it relates to turbine or axial fluid flow meters, especially suited for measuring flowing liquid. Such flow meters typically utilize magnets or magnetically attracted slugs that are radially disposed in a member that rotates with the rotor and induces a magnetic flux (induction or variable reluctance) in a fixed core spaced from and aligned with rotating magnets or slugs. The magnetic flux induced in the core in turn induces a signal in a coil wound about the core member which signal is transmitted to appropriate registering equipment. The radial displacement of the magnets from the rotational axis of the rotor is small compared with the average radius through which the fluid acts on the blades, thus enhancing the mechanical advantage of the meter and providing extremely linear low flow rate and low pressure preformance.
It is not intended, however, to restrict the present invention to this particular application, it being obvious that the present invention may be effectively employed in conjunction with different flow meter devices as well as other mechanical devices having turbines or rotors without departing from the spirit or scope hereof.
In the manufacture of turbine flow meters of the nature indicated above, it is desired that the rotor assembly, including the rotatable rotor element, be precisely centered within the bore or flow passage of a flow meter housing structure and that the axis of the rotor be oriented in precisely parallel relation to the linear direction of fluid flow, to enhance the mechanical advantage of the meter as much as possible to provide extremely linear low flow rate and low pressure performance which are qualities that are especially desired in both liquid and gas flow meters. To accomplish precise centering of the rotor assembly and to insure precisely parallel relationships between the axis of the flow meter and the flow of fluid through the meter assembly, it is typically required that spaced high quality precisely concentric surfaces be machined in a flow meter housing structure, which surfaces receive rotor assembly support elements to support the rotor assembly in positive relation to these concentric surfaces.
It is also necessary that the concentric surface be of precisely the same dimension so that each of the typically spaced rotor support devices may be precisely related to one another. Machining operations necessary to produce the high quality concentric and precisely sized cylindrical surfaces within flow meter housing causes the development of rather high manufacturing costs, but such costs, prior to development of the present invention, were deemed to be warranted in view of the desirability to provide a high quality flow meter construction having optimum low pressure performance capabilities. High costs of such machining operations is typically considered a necessity.
Accordingly, it is a primary object of the present invention to provide a novel flow meter construction incorporating a simple and efficient mechanism for achieving precise centering of a rotor assembly relative to a flow passage in a rotor housing structure, which does not necessitate the provision of high quality high cost machining operations.
It is a further object of the present invention to provide a novel flow meter construction wherein concentric bores or cylindrical surfaces may be formed in a flow meter housing by relatively low cost machining operations without sacrificing from the standpoint of accuracy in concentricity or positioning of the rotor within the housing structure.
It is also an object of the present invention to provide a novel flow meter construction wherein concentricity and positive alignment of the rotor assembly within a flow meter housing may be effectively maintained even though the spaced bores engaged by the flow meter supports are of different dimension.
Among the several objects of the present invention is noted the contemplation of a novel flow meter construction having means for supporting a rotor assembly within a flow meter housing, which means react with the rotor assembly and with the housing structure to achieve precise centering and positioning of the rotor assembly during assembly of the flow meter construction.
It is another important object of the present invention to provide a novel flow meter construction wherein the internal parts of the flow meter construction including the rotor, the rotor assembly and the rotor assembly support system may be quickly and simply placed within a flow meter housing structure by relatively inexperienced personnel and may be quickly locked into precise assembly simply by simple adjustment.
It is an even further object of the present invention to provide a novel flow meter construction including an internal rotor assembly and rotor support mechanism that may be quickly and simply disassembled through the use of simple tools for purposes of repair or replacement of the internal parts of flow meters and other similar mechanical devices.
It is also an object of the present invention to provide a novel flow meter construction that may be repaired or adjusted in the field without any requirement for the use of specialized tools for disassembly or assembly thereof.
Other and further objects, advantages and features of the invention will become obvious to one skilled in the art upon an understanding of the illustrative embodiments about to be described and various advantages, not referred to herein, will occur to one skilled in the art upon employment of the invention in practice.